Chapter 39: The Book of al-Bay'ah
It was narrated that 'Abdullah bin Waqdan As-Sa' di said: "We came in a delegation to the messenger of Allah, each of us with a question to ask him. I was the last of them to come in to the Messenger of Allah, and I said: 'O Messenger of Allah, I have left people behind me, and they are saying that emigration (Hijrah) has ceased.' He said: 'Emigration will not cease so long as the disbelievers are being fought."'
Sunan an-Nasa'i 4172